Method of filtering a fuel oil



,' :2 h r r PatentedFeb. 12, 1963 3,077,449 METHDD 9F FILTERING A FUEL01L James H. Kirk, Dyer, lnth, assignor, by mesne assignments, toSinclair Research, Inc, New York, N.1., a corporation of Delaware NoDrawing. Filed Mar. 25, 1955, Ser. No. 495,935

2 Claims. (Cl. 208-251) V This invention-relates to fuel oils and inparticular relates to a method of producing fuels oils which areespecially useful for steam generating boilers, gas turbine engines andsimilar equipment.

'The petroleum materials normally employed as fuel for steam generatingboilers, gas turbine engines and similar equipment must be inexpensiveif, in the case of steam boilers and the like, they are to compete withalternative fuel such as coal and, in the instance of gas turbineengines, if the engine is to be competitive with other engines as asource of power., A particularly inexpensive petroleum material whichhas found use for these applications is known as residual stocGenerally, however, residual stock is highly corrosive, since sodium andother impuriities of crudes tend to concentrate in the residuals duringconventional refining procedures. For example, residual fuels usuallycontain some ash which causes corrosion of gas turbine nozzles andbuckets in addition to causing deposits to build up in the turbine. Ofthe various elements in th ash, sodium is one of the most undesirable.Accordingly, a gas turbine manufacturer has specified that the turbinefuelshould not contain morevthan 10 parts per million of sodium and,preferably, not more than 5 parts per million. Treatment of residualsdesigned to correct the corrosion characteristics, such as 'de-s'altingarid washing, affects the cost of the resulting fuel to an undesirableextent. The instant invention relates to a method for producing a fuelcomposition from residual stock in'an' inexpensive andellicacious'manner. where the resulting fuel contains less than aboutparts per million of sodium.

I have now discovered a method whereby residual stock can be treated toresult in a significantly less corrosive fuel, which isless expensivethan prior art metheds. The method is effected by passing a dry residualstock through a filter having an average porosity not greater than about40 microns. Fuels produced in accordance with my method arecharacterized by significant reduction in sodiumcontent, that is to asodium content below 10 p.p.m., and hence in the corrosivity theynormally would evidence in use. Preferably, I reduce the sodium contentto less than about 5 ppm. to mak it a more acceptable fuel. The residualstock treated by this invention in general contains more than about 5p.p.m. of sodium since if it contains a substantially lesser amountthere is little need for its treatment in meeting the most rigorousspecifications now in effect. The feed may contain less than 10 p.p.m.of sodium and in such case the sodium content will be further reduced.The method also remo'es other contaminants such as lead and iron and thefinal composition frequently shows better anti-corrosion properties thanare attributable solely to sodium removal.

The filtering step of my invention can be effected with a variety ofdilferent filter materials. Particularly satisfactory results have beenachieved with both sintered glass filters and blotter paper. Regardlessof the composition of the filter material employed, etfective operationof my method requires that the porosity of the filter material be belowa certain limit. Thus, the average filter porosity must be such thatmaterials having a dimension of more than about 40 microns will not passthrough the filter; that is, the filter pores must have an average sizewhich is not greater than about 40 microns. The lower limit which can beemployed is limited solely by the existence of perceptible porosity andfilter rates which are tolerable. I have successfully used filtershaving a porosity of as little as 4.5 to 5 microns; it is preferred,however, to employ filters of about 10 to 40 micron porosity.

The filter can be employed in any manner desired. Gravity flow can beused but it is more desirable and is preferable to use a common filterpress with a pressure head being maintained on the residual stock, forexample of from about 20 to p.s.i.g. Other pressures can be employeddepending on the choice of the operator and the equipment available. Afilter aid can be employed in my process and can be any of thecommercially available filter aids so long as they do not deleteriouslyaffect the process. Especially satisfactoryfilter aids include High Flowand Sil-O-Cel (proprietary products of the lohns-Manville Co.), andgenerally consist of diatomaceous earth. Generally, from about 0.01 to1.0 Weight percent of the filter aid, based on the residual stock, isslurried with the oil. I prefer to employ about 0.03 to 0.07 Weightpercent, and particularly 0.05 Weight percent.

Fuel materials which canbe treated in accordance with my process includematerials commonly marketed as heating fuels, gas turbine. fuels and thelike. In general, these are known as residual fuels" and are customarilyobtained as pressure pipe still tars resulting'from thermal cracking, asstill bottoms from vacuum flashing topped crudes, bottoms from catalyticcrack-ing operations and viscosity breaking operations, and the bottomsresulting upon distillation of crudes at atmospheric pressure.Commercial examples include ASTM No. 5 and No. 6 heating fuels. Residualfuels are derived from various crudes, for example, naphthenic,paraffinic, Mid- Continent crudes and others.

The residual stock to be filtered in the manner of my invention must besubstantially completely dry. While an absolutely anhydrous state is notessential, it is preferred that no detectable water be present whentested by distillation dryness procedures. Frequently residual stocksare characterized by the degree of dryness necessary for practicing theinstant invention due to their source or previous treatment.

Where, however, wet stocks are to be treated, dehydration to dryness canbe-effected in any manner desired. Suitable methods include passing thestock through lines containing desiccants, placing desiccants in storagetanks which are employed for stock awaiting treatment,=raising thetemperature of the stock to "above the boiling point of Water whileagitating to insure escape of the wateras steam andsimilar methods. Preferably, the residual stock is maintained, during filtration, at atemperature of about 212 to 300 F to aid in securing fairly rapidfiltration rates; accordingly, dehydration of wet stock by simplyraising the temperature and agitating is an especially advantageous andpreferred procedure since preheat and dehydration areaccomplishedsimultaneously.

'Sodium, p.p.m

The invention will be described further by means of the followingexamples. It should be understood that the specific details disclosedare not to be construed as limiting the invention.

A No. 6 residual heating fuel was employed in Examples I and II. Thefuel had the following properties.

A sample of the No. 6 fuel oil was dehydrated by heating to 250 F. in avessel while agitating the oil. High Flow filter aid was slurried withthe oil in an amount equal to 0.5 pound of filter aid per 100 pounds ofoil. The slurry was then filtered in a press using blotter paper havingless than 40 micron porosity as the filter. The filtered oil wasfortified to substantially the original level with magnesium naphthenateto inhibit against corrosion 'by vanadium and tested in a gas turbinefuel corrosion burner. Analysis of the fortified sample compared to theunfiltered stock and the corrosion data obtained are:

TABLE II Unfiltered Stock Filtered Metal Analysis and FortifiedMagnesium Vanadium Calcium Aln'rnimlm Chromium Ir Lea Corrosion (GasTurbine Fuel Corrosion Burner-100 hrs.):

1,400 F., Loss, mgs 1,600" F., Loss, mgs

Example 11 'oil in an amount equal to 0.5 pound per 100 pounds of oil.The slurry was then filtered in a press using blotter paper having lessthan 40 micron porosity as the filter. The filtered oil was fortifiedwith magnesium naphthenate as in Example 1. Analysis of the fortifiedsample compared to the unfiltered stock and the corrosion data obtainedare:

TABLE III Metal Analysis Before Filtering After Filtering Sodium, p.p.mMagnesium... Vanadium Calcium-.. Load Ohrnminm Ir n Aluminum CopperCorrosion (Gas Turbine Fuel Corrosion Burner-100 hrs.):

1.400" F., Loss, mgs 1,500 F., Loss, mgs. 1,600 F., Loss. mgs..

The corrosion data and the reduction in sodium values as shown in Tables11 and III clearly demonstrate the effectiveness of my invention withboth regular heating oils and high sodium content heating oils.

5 Example 111 Samples of a No. 6 heating oil were filtered underidentical circumstances except for changes in porosity of the filteremployed. Eifectiveness of the various filters in 10 removal of sodiumwas noted by analysis of the filtrate.

The results are:

TABLE IV Porosity, Sodium in Sintered Glass Filter Microns Filtrate,

p.p.m.

Charge Oil. 12-15 Coarse 40-60 11 Medium. 10-15 3 Fine 4 5-5 1 Coarseprecoated with ter 40 2 l Johns-Manville High Flow.

From these data it can be observed that the filter having an averageporosity exceeding the limit established for my invention was notefiective in removing sodium while the filters conforming to theinvention reduced the sodium content satisfactorily.

Example I V A No. 6 heating fuel was filtered with and without a filteraid to demonstrate the value of a filter aid in the process. One-half ofthe oil was filtered through double sheets blotter paper while the otherhalf was filtered under the same conditions but with the addition of 0.5pound of High Flow filter aid per pounds of oil. The results obtainedare:

Example V In other runs employing filter aid and different pressures onthe filter press, No. 6 fuel oil containing about 0.054 pounds of HighFlow filter aid per 100 pounds of oil (111 grams of High Flow added to436 pounds of the oil) was filtered using blotter paper with a porosityof less than 40 microns. One run was conducted at a pressure of 60p.s.i.g. and the other at 20 p.s.i.g. The feed, samples taken from thefirst few pounds of filtrate and samples of the last few pounds offiltrate for each run were analyzed for sodium content. The data are:

TABLE VI Sodium, p.p.m. Feed 12-15 First filtrate at 20 p.s.i.g 6 Lastfiltrate at 20 p.s.i.g 3 First filtrate at 60 p.s.i.g 3 Last filtrate at60 p.s.i.g 3

From the data of Tables V and VI it is apparent that the use of filteraid is advantageous even in therelatively small amounts employed inExample V.

Example VI TABLE VII Sodium in Charge Stock Porosity, Filtrate,

Microns p.p.1n.,

Before Dehydration-Filter Type:

Coarse.--" 40-60 13.5 Medium- -15 12. 5 Fine 4. 5-5 Coarse precoatedwith High Flow filter aid. 40 13 After Dehydration-Fi1ter Type:

Fine 4. 5-5 1. 5 Coarse precoated with High Flow filter aid 40 7. 5

1 Would not go through filter.

I claim:

1. The method of producing a non-corrosive residual fuel in whichmagnesium is added to the fuel, the improvement which comprises passinga dry residual oil stock as a slurry containing about 0.01 to 1.0 poundof filter aid per 100 pounds of oil filtered through a filter having anaverage porosity of not greater than about 40 microns, the resultingresidual fuel being decreased in sodium content, containing less than 10parts per million of sodium and having substantially reduced corrosiveproperties.

2. The method of claim 1 wherein said dry residual oil is maintained ata temperature of about 212 F. to 300 F. during filtration.

References Cited in the file of this patent UNITED STATES PATENTS2,067,345 Roberts et a1. Jan. 12, 1937 2,174,265 Holt Sept. 26, 19392,179,028 Alton Nov. 7, 1939 2,296,850 Harrison Sept. 29, 1942 2,789,695Winkler et al Apr. 23, 1957 2,789,696 Jahnig et al Apr. 23, 1957 FOREIGNPATENTS 517,222 Belgium Feb. 14, 1953 OTHER REFERENCES Filtration WithFilter-Gel, publication by Celite Products Co. (copyrighted 1923), pages1 to 11.

Desalting Crude Oils (Eglofi et al.), Petroleum Tech nology, May 1938,pp. 19-20.

lhemical Refining of Petroleum (Kalichevsky), Reinhold Publishing Co.(New York), page (1942).

1. THE METHOD OF PRODUCING A NON-CORROSIVE RESIDUAL FUEL IN WHICHMAGNESIUM IS ADDED TO THE FUEL, THE IMPROVEMENT WHICH COMPRISES PASSINGA DRY RESIDUAL OIL STOCK AS A SLURRY CONTAINING ABOUT 0.01 TO 1.0 POUNDOF FILTER SAID PER 100 POUNDS OF OIL FILTERED THROUGH A FILTER HAVING ANAVERAGE POROSITY OF NOT GREATER THAN ABOUT 40 MICRONS, THE RESULTINGRESIDUAL FUEL BEING DECREASED IN SODIUM CONTENT, CONTAINING LESS THAN 10PARTS PER MILLION OF SODIUM AND HAVING SUBSTANTIALLY REDUCED CORROSIVEPROPERTIES.